Photochemical reaction paths of cis-dienes studied with RASSCF: the changing balance between ionic and covalent excited states
Author(s)
Santolini, V
Malhado, JP
Robb, MA
Garavelli, M
Bearpark, MJ
Type
Journal Article
Abstract
The balanced description of ionic and covalent molecular excited electronic states still presents a challenge for current
electronic structure methods. In this contribution, we show how the restricted active space self-consistent field (RASSCF)
method can be used to address this problem, applied to two dienes in the cis conformation. As with the closely related
complete active space self-consistent field (CASSCF) method, the construction of the orbital active space in the RASSCF
methodology requires the a priori formulation of a physical or theoretical model of the system being studied. In this article,
we discuss how the active space can be constructed in a guided and systematic way, using pairs of natural bond orbitals
as correlating partner orbitals (oscillator orbitals) and semi-internal correlation. The resulting balanced description of the
covalent and ionic valence excited states – with the ionic state correctly lower in energy at the Franck–Condon geometry –
is suitable to study the photochemistry of these and other molecules.
electronic structure methods. In this contribution, we show how the restricted active space self-consistent field (RASSCF)
method can be used to address this problem, applied to two dienes in the cis conformation. As with the closely related
complete active space self-consistent field (CASSCF) method, the construction of the orbital active space in the RASSCF
methodology requires the a priori formulation of a physical or theoretical model of the system being studied. In this article,
we discuss how the active space can be constructed in a guided and systematic way, using pairs of natural bond orbitals
as correlating partner orbitals (oscillator orbitals) and semi-internal correlation. The resulting balanced description of the
covalent and ionic valence excited states – with the ionic state correctly lower in energy at the Franck–Condon geometry –
is suitable to study the photochemistry of these and other molecules.
Date Issued
2015-07-18
Date Acceptance
2015-02-27
Citation
Molecular Physics, 2015, 113 (13-14), pp.1978-1990
ISSN
1362-3028
Publisher
Taylor & Francis
Start Page
1978
End Page
1990
Journal / Book Title
Molecular Physics
Volume
113
Issue
13-14
Copyright Statement
© 2015 The Author(s). Published by Taylor & Francis.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/Licenses/by/4.0/), which permits unrestricted
use, distribution, and reproduction in any medium, provided the original work is properly cited.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/Licenses/by/4.0/), which permits unrestricted
use, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Commission of the European Communities
Grant Number
302639
Subjects
Science & Technology
Physical Sciences
Physics, Atomic, Molecular & Chemical
Physics
RASSCF
sigma pi correlation
natural bond orbitals (NBOs)
ionic states
oscillator orbitals
semi-internal correlation
cyclopentadiene
cis-butadiene
DENSITY-FUNCTIONAL THEORY
CONSISTENT-FIELD METHOD
AB-INITIO CALCULATIONS
CONICAL INTERSECTION
ORGANIC-PHOTOCHEMISTRY
ELECTRON CORRELATION
REACTION PATHWAYS
POTENTIAL-ENERGY
SINGLET-STATES
BUTADIENE
Publication Status
Published